Accurate and timely information can be crucial to success in military operations, but in some circumstances, information can be gained only at considerable risk to personnel. In recent times, remote sensing has assumed certain intelligence gathering tasks. Not all desirable information is, however, accessible via remote sensing, and personnel continue to be in harm's way. One example is personnel swimming ashore and moving inland through hostile territory to gather timely information on enemy strengths and positions, which can expose the personnel to situations with the enemy, such as capture and attack. Another example is the placing of neutralization charges on submerged mines, which often can be at least partly covered with sediment and, therefore, difficult to neutralize. Thus, devices that reliably replace human operatives in gathering information or neutralizing mines may be desirable.
In the case of underwater mines, sediment covering a mine can shield it against efforts by divers or dolphins to place an explosive charge in close proximity to neutralize the mine. As a result, a large unwieldy neutralizing charge is typically carried and placed by hand over a buried mine. Despite such close placement, a sediment-covered mine may not be effectively neutralized because of the shielding effect of the overlying sediment. These techniques expose divers and/or dolphins used for this task to considerable risk.
Navigation can pose a challenge in an underwater environment, especially when land use is also desired, such as in intelligence gathering. Swimming, ambulating and/or digging impose different design constraints on a device. Designs for amphibious activity by a machine, therefore, necessarily reflect compromises. The study of biological mechanics reveals that designs for swimming in fish and in aquatic mammals have independently converged on fins, with some fish and animals also using their fins to dig or to move about on land. Terrestrial animals, such as frogs or otters, which operate secondarily in water, retain leg morphology suited to terrestrial locomotion and use webbed feet for enhanced swimming. In either machine or animal, current morphology can be seen to reflect design for the primary or first inhabited environment as well as the balance of time spent in water vs. on land.
Considerable effort has been devoted to developing robots that can operate autonomously on land. Some proposed terrestrial robots use legs with numerous degrees of freedom that require considerable sensing and computation to control their use, making movement slow and costly. Others propose extending compliant legs with low degrees of freedom to contact the substratum. Still others propose a stiff propelling component resembling and operating like a wheel rim portion supported by one or more spokes. Proposed leg and wheel-resembling appendages are inefficient for swimming. Such designs may not be well-suited for movement in water or other fluid environments.